According to the prior art, tires are molded and vulcanized by introducing the tire blanks into a spraying booth in which they are made to rotate by means of mechanical devices. A spray-gun is introduced into these rotating blanks and distributes a release agent solution on the inside of the blanks. The overspray is removed by means of vacuum or a water wall. The blank is then molded and vulcanized in a vulcanization press by means of a heating membrane (bag, bladder) whose task is to heat the tire blank, effect the vulcanization and press the tire at high pressure into negative molds (cf. the description of this procedure in DE-PS 29 25 662, DE-OS 31 46 053 and in particular the introductory part of published European patent application 0 111 100). In published European patent application 0 111 100, to avoid the disadvantages of this procedure, a process for the molding and vulcanization of tires and other rubber articles is proposed in which the heating membrane is provided, prior to the molding and vulcanization, with a cross-linked, cured, firmly-adhering elastic film of release agent that is bonded to the substrate by chemical interactions. However, the full benefit of the advantages to be achieved thereby are enjoyed only if the use of a release agent between the outside of the tire blank and the metal mold of the vulcanization press is not necessary, as the application of release agent to the inside and outside of the tire blank is generally one operation. Many existing tire-production plants are so designed, however, that such an outside release agent cannot dispensed with. In addition, the coating of the heating membrane as per European patent application 0 111 100 with a film of release agent calls for a very careful procedure, as otherwise the film of release agent on the heating membrane may be prematurely damaged or detached, thus possibly causing the life of the heating membrane to be shortened and reject tires to be produced.
The internal and external spray solutions used as release agents in the conventional procedure in most cases comprise benzinous solutions of release effective substances, which contain mineral fillers and have a benzine or total organic solvents content of the order of about 70%. These release-agent solutions obviously damage the environment or require very great expenditure on apparatus if the environment is not to be polluted. Aqueous release-agent solutions have thus already been proposed. The principle was that as little water as possible was used together with release effective substances, mineral fillers, thickeners and stabilisers, so that as little water as possible has to evaporate when a film of release agent forms. Typical aqueous release agents of this type comprise, for example, about 60 wt. % mineral fillers including thickeners and stabilizers and about 40 wt. % aqueous silicone oil emulsion (about 5-20 wt. % silicone oil, remainder water). Quite apart from the environmental disadvantages of silicone oils, it has been shown that, after the application of these aqueous release agents, a skin forms, as a result of which the water evaporates only relatively slowly when the film of release agent develops.